As portable terminals have continued to be miniaturized, making them ever thinner and lighter, their portability has continuously improved over the years, resulting in a greater demand for portable terminals. In lockstep, additional features mounted on the portable terminals have also diversified.
Particularly, one such additional feature, the digital camera functionality, has recently become perceived by consumers as being indispensable. The digital camera functionality is now included in most portable terminals.
Such digital camera functionality may include, in addition to simply taking an image, performing a face detection operation for detecting a facial image from an input image captured through a camera, and then performing a variety of recognition operations such recognizing a smile, a blink or the like.
Additionally, conventional face detection methods include being able to resize frames into a variety of sizes and detect faces in all of the images in the resized frames. For example, such conventional techniques were developed by Paul Viola and Michael J. Jones and were disclosed in the paper entitled “Robust Real-Time Face Detection” issued in “International Journal of Computer Vision, Volume 57, Issue 2” in May 2004 (see the paragraphs before section 3 of the paper). Such conventional techniques, however, have a problem of requiring large amounts of calculations, and thus taking a lot of time to perform the face detection operation.